The role of the homeobox gene Prox 1 in chicken ear development was investigated in collaboration with Dr. J. Stone (University of Washington). It has been shown that sensorigenic and neurogenic regions of the avian otocyst are demarkated by dense and diffuse expression of Prox 1 protein, respectively, which suggests that Prox 1 may regulate genesis of sensory and neural tissues in the avian inner ear. In collaboration with Dr. J. Wilting (University of Freiburg, Germany) we demonstrated that Prox 1 is a marker for lymphatic endothelial cells in normal and diseased human tissues. We therefore recommend the use of Prox1 as a lymphatic endothelial cell marker in histological sections. Since Prox1 is expressed in some nonendothelial cell types such as hepatocytes and pancreatic epithelial cells, double staining with Prox1 and CD31 is the most reliable method to characterize lymphatic endothelial cells.